(a) Field of the Invention
The present invention relates to a plug-in hybrid electric vehicle, and more particularly, to a method and an apparatus for controlling a plug-in hybrid electric vehicle.
(b) Description of the Related Art
As is generally known in the art, a hybrid electric vehicle (HEV) uses an internal combustion engine and a battery power supply together to drive the vehicle. In other words, the hybrid electric vehicle uses power of the internal combustion engine and power of the motor which are efficiently combined to drive the vehicle. Recently, a plug-in hybrid electric vehicle (PHEV) has been researched in which a battery chargeable by an external power supply is mounted.
FIGS. 5, 6A, and 6B are exemplary graphs for describing a driving mode of a conventional plug-in hybrid electric vehicle according to the related art. As illustrated in FIGS. 5 and 6A-6B, the driving mode of the plug-in hybrid electric vehicle may include a charge depleting (CD) mode and a charge sustaining (CS) mode.
When the battery is charged by the external power supply, the driving mode of the plug-in hybrid electric vehicle is established as the CD mode and the plug-in hybrid electric vehicle is driven by electrical energy of the battery until a state of charge (SOC) of the battery reaches to a reference SOC. In particular, an engine may start when a demand power of a driver is greater than a predetermined power. When the SOC of the battery becomes the reference SOC, the driving mode of the plug-in hybrid electric vehicle is set to be the CS mode. Particularly, the plug-in hybrid electric vehicle is driven so that the SOC of the battery corresponds to a target SOC.
When the SOC of the battery is maintained to be greater than the reference SOC and the battery may again be charged by the external power supply, the setting of the CD mode is advantageous in energy efficiency independent of the traveling condition. However, when the battery is again charged by the external power supply when the SOC of the battery is equal to or less than the reference SOC, even though the SOC of the battery is greater than the reference SOC, the setting of the CD mode is not suitable in the energy efficiency under the specific traveling condition (e.g., expressway, uphill road, etc.).
The above information disclosed in this section is merely for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.